MINNEAPOLIS (WCCO) — University of Minnesota researchers, alongside top veterinarians and the Food and Drug Administration, want to know if the popular trend of grain-free dog food is contributing to an increase in a type of heart disease called dilated cardiomyopathy.

Among the families affected are Rob and Carol Salmon, of Minneapolis. Their dogs, Delaney and Blue, ate Perham-based NutriSource’s line of grain-free chicken and pea blend kibble for years. The Salmon’s gravitated towards NutriSource because of its local presence and perceived health benefits, being grain-free.

Now, it’s one of dozens of brands that fall under the criteria of what the FDA is investigating. The Salmon’s did not learn of the investigation until their dogs were already sick.

“I was in shock,” said Carol Salmon. “Because they seem normal. They seemed absolutely okay.”

Delaney and Blue both tested positive for taurine deficiency — an essential amino acid. They’re one of the FDA’s 158 cases, which makes up less than one percent of the number of dogs eating grain-free food.

“But there are many cases where if we’re not looking, how do we know that they have low taurine?” asked veterinary nutritionist Dr. Julie Churchill, from the University of Minnesota.

Churchill, along with nationwide studies at the University of California at Davis and Tufts University have a working theory that suggests it’s not the lack of grains making dogs sick, rather what companies put in place of it. Sweet potatoes, peas and other legumes might be stripping a dog’s ability to absorb the taurine.

“It’s not a complete common denominator, and that is what makes this so confusing,” said Dr. Churchill.

In a written statement, NutriSource told WCCO:

“Pets are family, and we would never knowingly provide products that could harm them. Our products are tested and approved by multiple independent authorities. We continue to proactively gather research and scientific data to ensure we are doing what is best for pets and following guidelines and recommendations set forth by the FDA, AAFCO (American Association of Feed Control Officers) and other experts in pet nutrition.”

NutriSource also told WCCO it started supplementing its diets with taurine, in hopes that it will aid dogs whether they are predisposed to DCM or already have it. Sometimes, for any of several reasons, that works. It did for Blue.

It did not for Delaney. Her heart was already too damaged.

“It’s hard to wrap your mind around that you have a dog that’s that sick when she doesn’t look that sick,” said Carol Salmon.

Dogs with DCM might show symptoms such as coughing, fainting and fatigue, however, some do not.

“They’re going along until they reach a certain point of no return,” said Churchill regarding dogs who show no symptoms. “That’s what I’m worried about.”

Facebook groups share that worry. Pages — some 11,000 users strong — search for answers and advice from foods and tests, to diagnoses.

Today, pet parents are left relying on the FDA’s guidance, or that of their local veterinarian.

“If it were grain-free or some of the exotic ingredients right now, I say do not feed them until we figure out what’s going on. It’s just not worth the risk,” said Churchill.

That’s different from the FDA, which does not advise dietary changes.

“The FDA’s maybe a little more conservative because we don’t know the answer,” said Churchill. “So they’re unwilling to say stop something, when there are dogs that have been eating grain-free diets that are not harmed.”

The Salmon’s changed Delaney and Blue’s dog food right after the diagnosis. But it may not be enough, even after an estimated $4,000 in tests and medication.

“And that’s my fear,” said Carol Salmon. “Even though we’re treating Delaney… it hasn’t increased that much with medication and taurine. So I’m not sure how long we’ll have her.”

So when can pet owners expect more clarity on the health of grain-free food?

UC-Davis and Tufts’ study is done, just waiting for peers to give it a final review. And the FDA told us it doesn’t yet have a timeline to when it will publish its report.

Tuesday on WCCO This Morning, we’ll have advice from pet health associations on what to look for in a quality bag of dog food.

So is there any way for dog owners to know if their pet is sick? If your dog shows symptoms, it will be coughing weakness and fatigue. You can also ask your vet about checking for a heart murmur, then possibly doing a taurine test or an echo.